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Early chronic administration of propranolol reduces the severity of portal hypertension and portal-systemic shunts in conscious portal vein stenosed rats
Early chronic administration of propranolol reduces the severity of portal hypertension and portal-systemic shunts in conscious portal vein stenosed rats
We investigated the effects of early cnronic administration of propranolol on systemic and splanchnic hemodynamic changes, and the developmen.! of port&systemic shunts in conscious, unresttamed, portal vein stenoscd rats. Compared to rats receiving placebo, early chronic propranolol (75 mg kg-’ day-‘) admmlrtrarion ro rats begun 3 days before portal vein stenosis and then continued for 10 consecutwe days, resulted m a sqmficant decrease in both portal pressure (11 6 + 1.5 mmHg) and portal-systemic shon:s (48 f 18%) which wete measured 2 to 3 h after the final dose of proprarnlol (IS.?. C 1.5 mmHg and 84 + 590, respectively). These beneficial effects were also observed 18 to 24 h aher the final dose of chronic propranolol. In rats given propranolol continuously for 5 days starting 5 days after portal vein stenosis. portal pressure (11.8 f 1.2 mmHg) was significantly lower than in the placebo group hut portal-systemic shunts (76 f 14%) were not significantly different. In rats receiving a single dose of propranolol (75 mgikg) 10 days after portal vein stenosis and measured 2 to 3 h after propranolol administration, portal pressure (12.8 f 1.0 mmHg) was significantly lower than in the placebo group. Portal-systemic shunts (72 + 17%). however, showed no significant difference from the placebo group. Similar values in portal pressure (23.3 f 1.2 mmHg) and portal-systemic shunts (83 -f: 21%) were also observed in rats 18 to 24 h after a single dose of propranolol. In addition. although propranolol administration did not alter hepatic artery blood flow, the fraction of cardiac output reaching the liver increased significantly after chronic propranolol administration. We &so demonstrated that chronic propranolol adminisrration srarted before port11 vein stenosis limited the initial rise m putal pressure which follows portai vein stenosis. We concluded that early chronic propmnolol administration reduces the severity of portal hypertension and portal-systemic shunts in portal vein stenosed rats. These beneficial effects are probably a result of a limited initial increase in penal pressure immediately following portal vein stenosis.
Propranolol has hecn shown to have significant benefits in preventing variceal hemorrhage (l-3). It is also well established that propranolol reduces ponnl pressure both in cirrhotic patients (4-61 .md in portal hypertensive dnimais (7.8). However, most previous hemodynamic studies have been performed in humans or animals with well developed portal hypertension and pottaCsystemir coliateralr. Recent preliminary results suggest that the development of penal-systemic shunts in portal hypertensive animals might he prevented by early pharmacotherapy
w:h p;opranolol(9,10). In these previous studiea. however, cxpcnments were performed under general anesthesta and no blood flow measurements. wcx obtained (9.10). Thus, the aim oithe present study was to evaluate the potenttxl beneficial effects of ezr!y, chronic administration of propranolol on systemtc and splanchnic hemodynamic changes end ie preventing ti:e developmenr of port&syrtem:c Gnu;. m conscious, umestramed poiid “et” steno& rats.
214
I-KC
Materials
catheter was introduced
and Methods
UN
et
at.
mt” the left ventricle via the right
carotid artery for radioactive
microsphere
injection.
Cor-
rect positioning of the catheter was confirmed by pressure
Adult
male Sprague-Dawley
riobin-IL-Elbcuf,
France)
rats (Charles
River.
St
t,a..mg.
A femoral
weighing h .twcc”
280-330
g
mmitor
arterial pressure and heart rate. and to withdrnw
were studied. Portal hypertension vem s?enosis as prewously
‘ne
VW induced by portal
descrioed (8).
Briefly,
median tapa,“tomy.
A polyethylene
diameter
(Biotrol
Paris,
France)
mca~“rcment~
was
placed along the length of the portal vein, and 3-O silk was
with catgut.
All
cycle, and allowed
and the mesentcric
room at irce ac-
cess to food and water.
pm
component
U.S.A.)
stability,
““Cc-labeled
(New
England
microspheres
Nuclear,
Boston,
the microspheres
part, seven groups of six rots were studied. A first group
sample was withdraw”
of ““rmat
into B motor-driven
rots rewed as control. Three days before portal
vein stenosis and then continuously
for
10 c~nse~~ti~e
days, two groups of rats received propranolol day-’ by gavagc. A preliminary oral administration significant
A precounted
sive rats (II).
mg kg-’ day-’
effects as “on-portal
Hemodynamic
studies
were
injection,
aliquot of 0.1
quantified
had
from the femoral
hyperten-
ton, MA,
performed
blood
artery catheter
after the hemodynamic
microspheres
U.S.A.)
mcasorcments.
of portal-systemic
as described by Geraghty
“3Sn-labeled
Starting 5 s
the reference
syringe at a rate of 0.8 mllmin for 1
the mesenteric component
study showed that chronic
of propranolol75
hemodynamic
min. Immediately
75 mg kg-’
MA,
was injected and flushed with
0.5 ml saline over 30 s into the left ventricle. before
of 15
were suspended in 10% dextralp and sonicated
ml (==&l Ooo microspheres)
In the first
of portal-
81 least 1 h of consciousness with quiet rest and
in diameter
for 10 min prior to injection.
Two types of experiments were performed.
was then
vein for pressure
distal part of the superior mesenteric vein. hemodynzni:
was closed
rats were caged in an doimal
24 “C, with a 12-h light-dark
abdomen
via a smsll ilwl
systemic shunts. Tne tip of the catheter was placed in the After
used to ligate hoth the catheter and the portal vein. The catheter waz then removed and the abdomen
The
sample.
vein was cannulated
catheter of 0.96 mm
Phama,
blood
,cfcrencc
was also inserted to
opened via a midline incision, and the superior mesenteric
under
ðyl ether anesthesia. the portal vein was exposed after external
artery cathether
shunts was
et al. (12).
(New England
Briefly,
Nuclear,
Bos-
of 15nm in diameterweresuspendedin
10% dexrran. After sonication for 10 min, 0.15 ml miero-
either 2 to 3 h (chronic 2-3 h) or 18 to 24 h (chronic 18-24
spheres suspension (=@I @M microspheres)
h) after the final dose of propranolol. A fourth group of __.. .____. _^^“:.._rl .“._) __ ;‘z-ah^ (saline) by garage for 10 conscc-
and flushed with 0.4 ml saline into the portal venous ~1%
utivc days. Ten days &cr
riod of 20 s.
wrtal
vein stenosis. the other
two groups of rats r”ccived o single dose of prapranolol75 mg/kg by gavage. Hemodynamic
tern via the superior
mesenteric vein catheter “vc,
a pe-
The animals were then killed with pentobarhital,
and
individual
studies were pertarmed
were iojected
organs were dissected ““t. The radioactivity
of
either 2 to 3 h (acute 2-3 h) or 18 to 24 h (acute 18.-24 h)
each organ and the reference blood sample were counted
after proprznolol
in a gamma
ndministration.
received prapranolot
The last group of rats
4000,
75 mg kg-’ day-’ by gavuge smrting
5 days after portal vein stenosis and then continuously
for
scintillation
Intertechnique,
eoonte,
P&i,,
(Lompteur
France).
Gamma
Adequate
sphere mixing was assumed when the differene
microa: radio-
5 consecutive days. Only portal prcr~ure and portal-sys-
activity between the left and right kidney was below 10%.
temic shunts were measured 2 to 3 h after the final dose of
Five animals did not meet this requirement
propran”l”l
jected from analyses.
In the second part, measurements
continuous
dally portal
pressure
we.e taken in I6 conscious. unrestrained
Cardiac formula:
“utpur
(CO)
CO (mllmin)
was calculated = [radioactivity
rats. Three days before portal vein stenosis, rats received
ference sample radioactivity
enher prooranol”l75
diac index (CI)
mg kg-’ day-’ (n = L,) or placebo (n
= 8) by gavagc and then continuously days. Portal pressure was neasured
CI (mlmm-~~100
:or 3 consecutive
and recorded
every
24 h after initial portal vrm itcoosis.
g-t body wt.) = CO/100
gional blood tlow was calculated
tributary
“ndei
diethyl
ether anesthesia.
a
blood
splren, stoowh, creai
blood
flow
.
iniected
(6Tp.F)
small howl,
flows.
Portal
Car-
formula:
g body wt. Re-
according to the follow.
in8 formula: “r8an blood flow (ml/min)
Blood f7ow and mcsenreHc-.rysrrmic shunr rnemurenwnls. All rntr were fa\ted I8 h before the studier hilt had to water.
injected (cpm)irc-
x 0.8 (mllmin).
was derived from the following
tivity (c”mYradioactivitv
free izce”,
@pm)]
and were re-
by the following
= [organ ,a
(corn)1 x CO.
ioacPortal
..I.
was taken
as the sum of
colon, melentcry
tributary
blood
ftcw
and panwas ex-
pressed in ml~min~‘~100 g-’ body wt. Systemic vascc!*:
?i5
resistance (SVR) was calculsted according to the following formula: SVR (dyws-cm-’ x IO’) = [mean attetwl pressvrz (iMAP (rrmlig)) x aO]/CO. Portal tributary “2s. cular tesistance (F WR) ws calalated as follows: PTVR (dyn.s.cm-’ x III’) = ([?AAP - portal pressure (PP (mmHg))] x BO)WTRF. Hepatocollateral vascular rcsistance (HCR) was :alculated as follows: HCR (dynwtr5 x ld) = (PP x gO)/PTBF. Hapatic fraction of ponal fiow (HFP) was calculated as follows: HFP = PTBF-(PTBF x MSS%) expressed as mlmin-‘,g-’ Iwer wt. Total hepatic blood flow (THBF) was calculated as follows. THBF = HFP + hepatic anery hlood tlow expressed as ml.min-‘.g-’ liver wt. Fractional hepatic blood flow (FHBF), which was the percentage of cardiac output reachirg the liver per mm. was calculated as follows: FHBF(%) = (THBRCO) x 100. In order toobtain a b.t ter Statistical analysts tot hepatic artery blood flow, hepatic Raction of portal flow, total hepatic blood flow. and fractional hepatic blood flow, we combined all tats recet”. ing early chronic propranolol administration s:arted before portal vein stenosis (n = 12). all rats teceivmg acute propranolol administration (n = I?) and compared them with the pldll?bo and the normal group. The degree of mesenteric-systemic
shunts (MSS) “2.i
calculated using the following fotmula: MSS (%) = [lung radioactivity (cpm)/li”er + lung radioactivity (spm)] x 100. The reprcducil~ility of MMS was measured in three consciaus unrestrained portal hypettsnsive rxs The coefficient of “atiabJity (xcand tneasuretttent - first measurement) x lOO/tirst measurement) was 35 f 14%
LX,+ purt,,l ,,rerru,e ,nell~tvw,te,tl. After 3 days of e thcr proprx~olol or placebo :xdwinistration. a media I:qx!rotomy war performed under diethyl ether anecthesia. Chronic cannulation of the portal “em was performed a~ previously dcrcribed (!3). A silastic tube of 0.M mm cxtetnal diameter (Dow Corning Cotporatmn, MI, U.S A ). connected to a 0.96 mm po!“ethylene catheter ws inserted into a small ileai vein and then gently advanced to the bifurcation of the supenor mesenrxic vein and splemc vein. Through the ,““ctmn of the .~I.stic and polyethylene tube, the catheter “as Faxed to the ntesentery with 3-O silk. and baseline portal pressure was measured and recorded with a pressure moni!or (Philips CM 1311.The Netherlands). After obtaining the baseline partal pressure. penal vein stenosis was performed as described xbove. The abdomir,al wall was closed with cat@, and the polyethylene
catheter
was brought out thrcwgh a
cubcutaneous tunnel and fixed to the ammal‘s neck. Iite tats were housed in individual cages with free access to food and water. Pottal ptexure was mez;ured every 24 h for 3 days following initial portal “em stencs~. Vahd pressures were :btained *hen pressure tracing showed a :apid nse followed by a stable plateau with slight respiratory variation. and blood could be easily aspirated. Two tats itt each group ‘x..rc excluded since they dad not meet these criteria.
Results were expressed as mean + S.D. One-way anal“sis of variance with Dunnett‘s correction of multiple
216 comparison was used for statistical analysk. Correln:mns were examined by linear regression. p values < V.dS were considered statistically significant.
Results Aloodfloa nnd merentr-,~cic-sysremicshunr rnemvremen,~ Results of hemodyrmmic values am rhow” in Table 1. There were significant differuxa in portal pressure, mesenteric-systemic shunts, and hemodynarnic values between normal rats and portal vein stenosed rats receiving placebo. Mea” arterial ,,ressure wes not altered by ci!her acute or chronic proprsnolol administrm;on in rats compared to rats receivittg placebo. I” rats receiving cbro”:~ propranolol. cardiac index, heart rate. portal pressure, port;: tribzry blood flow, and me:en!s: c-s::z!cmir: shunts measured 2 to 3 h after the final dose of propranolol wre significantly reduced compared to rats receiving placebo. Systemic and portal tributary vascu$r resisrnnce increased rignificantls in rats receiving chronic propranoIxrbo group. On the other band, 101 compared rvbiler uodynmmc changes were four d in rets ?!O? single dose of propranolol compwed to the
! I! .
(1t’l t a
plac? o group. e”ll’ rc-systemi: inns.. 2 tu 3 ‘, ceiving a .r;,gle dynamic WI les
there was no signitsant difference in messhunts between the two groups. Fortheratrer proprairolol administration, rats redose of propranolol demonstrated hemosimilar to rats receivmg chronic proprano-
!L?!. At the same lime, mesenteric-systemic shunts were siguiiwantiy higher in rats receiving a single dose of propranolol :.nan in rats receiving earl! chronic pro~ranolol. Eighteen to 24 h after proprarnlol administration, compared to the placebo group. ran receiving chronic propranolol showed a sigi.ificant reduction in cardiac index, bear1 rate, po::al pressure, portal tributary blood flow,
and mesenteric-systemic shunts. Portal tributary vascular csistance increased significantly. I” rats receiving a sin. gle dose of propranolol. cardiac index. brat rate, portal pressure. and portal tributary blood flow measured lg to 24 h after prapranolol administration were also significantly reduced compared to the placebo group. At the same time, mesenteric-systemic shunts values were “early identical in these two groups and were without stati&aI significxxe. Moreover, 18 to 2,4 h after propranolol administr:ttion. portal pressure and mesenteric-systemic shunts values were signifkantly lower in rats that had received chronic propnmolol than in rats receiving a single dose of propranolol. In rats receiving propranolol for 5 consecutive days after pan-! vein stenosis, portal pressure 01.8 f 1.2 mmHe. li < 0.01) decreased sieoificantlv cun&ed to the placebo groop but there was no signif5 cant din’erence in mesenteric-systemic :;hu”‘-s (76 + 14%)
_.
between
,
I
,
the two groups.
Among rats receiving propranolol, either acutely or chrcnically, tbcre was a highly sign;ii.a”t correlation beiwee” cardiac index and portal tributary blood flow (n = 24, r = 0.84, I < 0.001). However. in rats rsceivine txopranolol, no correlatb-n was found between portal Pressure and portal tribuhry blood flow (n = 24, I = 0.04.p = -I
0.85). Hepatic artery blood flow, hepatic flow. total hepatic blood flow, and blood flow values are shown in Table nosed rats receiving placebo showed tions in hepatic fraction of portal flow,
fraction of portal fractional hepatic 2. Portal vein stesignificant reductotal hepatic blood
flow, and fractional hepatic blood flow compared to normal rats. On the other hand, compared to rats receiving placebo, portal vein stenased rats receiving chronic prapranolol showed significant increases in hepuic fraction of poRal flow, total he@ic hepatic blood Bow
blood flow, and tiacticmal
PROPRANOLOL
IN PREVENTING
PORTAL
WPERTENSION
217
s-udy. prop:ioolol Portal pressure changes after portai vem stenosis are shown in Fig.
1. Compared
to rats receiving
placebo,
ba.eline portal pressure decreased sigmficantly ce.ving propranolol
m rats re-
(5.8 + 1.2 vs. 7.3 f 0.8 mmHg.
p <
O.fl5l. On the 1st. 2nd. and 3rd dav. resoectivelv. ,a
after
1
portal
vein stenosis. rats receiving
rig,nificantly
lower penal
prcswre
propranolol
showed
than in rats receivmg
placeho (20.1 -r 2.7 vs. 2,;.2 + 2.2 mmHg. y < 0.05, 1X.3 f
1.5 mmHg. p < 0.01: and 16.6 +
1.6 vs. 21.7 f
I 7 vs.
was aJminis:crcd
by oral-gwric
vage which i: similar to the clinical sitution. propraoalz
or:d
in our rats, however.
differs from the
dose used in cl.nical investigations since propzmolol
me-
tabolism markedly differs amongrpenes. In the present study. a redwion porn-systemic
of tix percewqe
of
shunts was only observed in rats receiving
early chrome propranolol
begun &fore
portal vein steno-
sis. This effect was noted either 2 to 3 h or 18 to 24 h after the final dose of propran~:ol.
lo contrast. acute ado&w
trarion or contmootts administration
20.3 2 1.0 mmHg, p < 0.01; respectwely).
ga-
The dcse of
of propranolal
after
portal vein stenosis lowered portal pressure but had no etfeet on the percentage of portal-systemic over. hemodgxmtic
last dose r: proprwtolol In the present study,
wehave ciearly
early and chronic propranolol severity of portal portal-systemic Our
hypertension
of rats. rire
stndieq (o.10) and wppat
pothesis that early pharmacotherapy opment of prtal-systemic
of
vein steno&.
from a small number
mn~is,eo, with predow
Ihat
reduced the
and the developmen:
shunts in rats with portal
results. obtained
aniaals.
demonstrated
adminisrration
the hy-
prevents the de-&
shunts m portal
hyperteasive
In previous studies experiments were performed
under general
anesthesia
ments were obtained demonstrared
and no blood
(9.10).
flow
Furthermore.
mearoreit was not
whether the beneficial effects were a result
of chronic or acute administration
of propr~nolol.
In thtr
shunts. More.
values measured 18 IO 24 h atier rhe were similar
in rats recekang
chronic propranold
and in rats receiving a single dose of
propranolol,
portal
while
prescore and portal-systemic
chrmrs li’eie lower in mts recen’ing chrome propranolol ihan In rats receiving a single dose of prqxanolol.
The
lot’ percentage of shunting observed in rats receiving early and chronic propranolol oasis was probably
begun before portal vein ste-
due 10 a limitation
of the initial
c.edse in portal pressure whnch onmediately tal vein stenosis, i.e., pressure rea&ed
in rats receiving
24.2 mmHg
I day
in-
follows por-
placebo.
portal
after portal vein ste-
nosis. whereas it reachrd only 20.1 mmHg in ra:‘, receiving p:opranolcl.
In addition.
Gstec on the 2nd and3rd prewmabiy panolol portal
admmistration. hypertension
this beneficial
efLct
pcr-
day after portal vein stenosis and
on the following
days doe to continuous pro-
In other words, in this model of
in rats, the development
of p-anal-
systemic shunts depends mainly on t’le imtial elevattm
of
portal pressure. Similar observations have been pre\ IOUIy demonstrated
in rats vdth portal vein stcnosis (14 :5).
la these previous stt dies, a significant found between mesenteric-systemic
correlation
eter of portal vein stencsi~. and presumably, rise in portal pressure. significant relationship teric-systemic
the initial
previous studies also reported
a
bera een the percentage of mesen-
shunts and the value of portal
measured 2 weeks after portal \ein contrast,
was
shunts and the diam-
there was no correlation
pressure
stenosis (12.14).
In
berween splenic-gys-
temic shunts and the diameter of stenosis or the degree of portal hyperLtsion rplenic-syswnic
(14). The tack of correlation
shunts and portal
between
pressure may be re-
lated to the extensive splenorenal
shunting ;vhich occurs
with a moderate
hypertension.
:iiij:,
;ii::e
degree of portal
:EPC:C portA
bypencorioa
merenieric-systemionhuntsto In :his study, propmnolol
decreased portal
cardiac index. and portal tributary wiving propranolol,
In con-
ii necs.siary for
develop. preswre.
blood flow. In rats re-
since portal tributary
blood flow sig-
H.-C. UN
218
et at.
nifirantly correlated with the cardiac index, while portal
blood flow was not altezcd by propranolol
admin,stration,
prcssurc
wherea*,
increased
showed
blood tlrw.
no
correlation
with
portal
the decreased portal tributary
not only due to a decrease in cadiac outpa increase
in portal
been postulated
tributary
tributary
blood flow was but also to an
va~cuk+r resistance.
:hat the mcreaxd
portal tributary
activit)
or to the ,9,-bkxking Although
to 3
I >‘ter ‘ ither
pr~van~~lol
property
vascu-
chronic
cam increw:
group.
in hepatocollateral
Desprte the short half-life
vascular resistance
total
chronic
the liver
hepatic
hepatic
fraction
In rats receiving oI portal
flow
was also increased
ndmini~trati.m,
10
mals. From
the
shunts in these portal
precent
chronic proprarlolal portal
hyl rrwxion
study,
hypertensive
we coscludcd
administration
stall persisted. In the presence cf hypertensive
nuiui aiwr vrai administratmn
of propra-
aniearly
of ponal-rys-
effects probably
the systemic and splanchnic hemodynam-
thsr
reduced rhe degree of
and the deve!opmont
administration.
rats. a decreased ‘first pass’ heparic elimination
of par-
tal flow was in accordattce with the lower degree cf mes-
we at~o noted
shunts in these portal
by
suggestmg a better
temic shuctr in portal vein stenosed rats. The:t
ic effects of propranolot
placebo.
The increased hepatic fraction
that. 18 to 24 h after either acute or chronic propranolol
the penal-systemic
flow in-
with the rats receiGg
blood
propranolol
hepatic perfusion.
has been previously
patients (21).
enteric-systemic
of propranolol.
of propranolol,
propranolol,
after
of
there have been similar signifi-
to 2tJ min after intravenous administration
*caching
flow
In
chronic or acute oral administration
vere higher than in thk placebo
previous s! ‘ties (18,lU).
Thus,
2
blood
An increased fraction of the
in ciirbottc
creased in comparison
the mean
vz~scular resistance mearsred
hepatic
sdministratiun.
output
demonstrated
of propranolal
not s atistically significant.
values of he ~tocollaferal
cardioc
It has
lar resistance in rats is due to an unopposed a-adrenergic (8.16-18).
fractional
proprenalol
beneficial
resulted from a limited initial increase ill
portal pressure immed’ately sis. The application
follr,wing
portal vein steno-
of this treatment in man needs, how-
ever. to be investigred.
may enpiain these bernady-
namic changes. In the present study. we also demonstrated vein stenosed rats receiving Iov.ei total hepatic blwd tlow,
and fractional
rats. Although
placebo
+-!
+rtal
had a significantly
flow, hepatic fraction of portal
hepatic
blood
flow than iat normal
not stattstically significant,
the mean value
rf hepatic artery blood flow in portal vein stenosed
rats
receiving placebowas higher than in normal rats. A similar observation has been reported in a previous study (20). Consistem with previous result (8.16,18), in our investigation
in portal
vein stenoscd
rats, hepatic
artery
Dr. Lin WE supported government.
anli ‘ram
by a fellowship the Veterans
from the Frerlch
General
Haspital-
.
and iCd!ional Science Council. Taiwan. R.O.C. held a fellowsi5p from the Fonda&n poor la Recherche hl.Sdicale. This work was presented in part at the 41st annual meeting of the American Association
Taioei.
Dr. Soubrane
For The Study of Liver Disease, Chicago, IL, U.S.A., November 3-6, 1990; and was published in abstract form (Hepatology lY90,12:874).
PROPRANOLCL
IN PREYENTING
l’0RTc.1.
HYPERENSIC)N
21’)
We investigated the effects of early cnronic administration of propranolol on systemic and splanchnic hemodynamic changes, and the developmen.! of port&systemic shunts in conscious, unresttamed, portal vein stenoscd rats. Compared to rats receiving placebo, early chronic propranolol (75 mg kg-’ day-‘) admmlrtrarion ro rats begun 3 days before portal vein stenosis and then continued for 10 consecutwe days, resulted m a sqmficant decrease in both portal pressure (11 6 + 1.5 mmHg) and portal-systemic shon:s (48 f 18%) which wete measured 2 to 3 h after the final dose of proprarnlol (IS.?. C 1.5 mmHg and 84 + 590, respectively). These beneficial effects were also observed 18 to 24 h aher the final dose of chronic propranolol. In rats given propranolol continuously for 5 days starting 5 days after portal vein stenosis. portal pressure (11.8 f 1.2 mmHg) was significantly lower than in the placebo group hut portal-systemic shunts (76 f 14%) were not significantly different. In rats receiving a single dose of propranolol (75 mgikg) 10 days after portal vein stenosis and measured 2 to 3 h after propranolol administration, portal pressure (12.8 f 1.0 mmHg) was significantly lower than in the placebo group. Portal-systemic shunts (72 + 17%). however, showed no significant difference from the placebo group. Similar values in portal pressure (23.3 f 1.2 mmHg) and portal-systemic shunts (83 -f: 21%) were also observed in rats 18 to 24 h after a single dose of propranolol. In addition. although propranolol administration did not alter hepatic artery blood flow, the fraction of cardiac output reaching the liver increased significantly after chronic propranolol administration. We &so demonstrated that chronic propranolol adminisrration srarted before port11 vein stenosis limited the initial rise m putal pressure which follows portai vein stenosis. We concluded that early chronic propmnolol administration reduces the severity of portal hypertension and portal-systemic shunts in portal vein stenosed rats. These beneficial effects are probably a result of a limited initial increase in penal pressure immediately following portal vein stenosis.
Propranolol has hecn shown to have significant benefits in preventing variceal hemorrhage (l-3). It is also well established that propranolol reduces ponnl pressure both in cirrhotic patients (4-61 .md in portal hypertensive dnimais (7.8). However, most previous hemodynamic studies have been performed in humans or animals with well developed portal hypertension and pottaCsystemir coliateralr. Recent preliminary results suggest that the development of penal-systemic shunts in portal hypertensive animals might he prevented by early pharmacotherapy
w:h p;opranolol(9,10). In these previous studiea. however, cxpcnments were performed under general anesthesta and no blood flow measurements. wcx obtained (9.10). Thus, the aim oithe present study was to evaluate the potenttxl beneficial effects of ezr!y, chronic administration of propranolol on systemtc and splanchnic hemodynamic changes end ie preventing ti:e developmenr of port&syrtem:c Gnu;. m conscious, umestramed poiid “et” steno& rats.
214
I-KC
Materials
catheter was introduced
and Methods
UN
et
at.
mt” the left ventricle via the right
carotid artery for radioactive
microsphere
injection.
Cor-
rect positioning of the catheter was confirmed by pressure
Adult
male Sprague-Dawley
riobin-IL-Elbcuf,
France)
rats (Charles
River.
St
t,a..mg.
A femoral
weighing h .twcc”
280-330
g
mmitor
arterial pressure and heart rate. and to withdrnw
were studied. Portal hypertension vem s?enosis as prewously
‘ne
VW induced by portal
descrioed (8).
Briefly,
median tapa,“tomy.
A polyethylene
diameter
(Biotrol
Paris,
France)
mca~“rcment~
was
placed along the length of the portal vein, and 3-O silk was
with catgut.
All
cycle, and allowed
and the mesentcric
room at irce ac-
cess to food and water.
pm
component
U.S.A.)
stability,
““Cc-labeled
(New
England
microspheres
Nuclear,
Boston,
the microspheres
part, seven groups of six rots were studied. A first group
sample was withdraw”
of ““rmat
into B motor-driven
rots rewed as control. Three days before portal
vein stenosis and then continuously
for
10 c~nse~~ti~e
days, two groups of rats received propranolol day-’ by gavagc. A preliminary oral administration significant
A precounted
sive rats (II).
mg kg-’ day-’
effects as “on-portal
Hemodynamic
studies
were
injection,
aliquot of 0.1
quantified
had
from the femoral
hyperten-
ton, MA,
performed
blood
artery catheter
after the hemodynamic
microspheres
U.S.A.)
mcasorcments.
of portal-systemic
as described by Geraghty
“3Sn-labeled
Starting 5 s
the reference
syringe at a rate of 0.8 mllmin for 1
the mesenteric component
study showed that chronic
of propranolol75
hemodynamic
min. Immediately
75 mg kg-’
MA,
was injected and flushed with
0.5 ml saline over 30 s into the left ventricle. before
of 15
were suspended in 10% dextralp and sonicated
ml (==&l Ooo microspheres)
In the first
of portal-
81 least 1 h of consciousness with quiet rest and
in diameter
for 10 min prior to injection.
Two types of experiments were performed.
was then
vein for pressure
distal part of the superior mesenteric vein. hemodynzni:
was closed
rats were caged in an doimal
24 “C, with a 12-h light-dark
abdomen
via a smsll ilwl
systemic shunts. Tne tip of the catheter was placed in the After
used to ligate hoth the catheter and the portal vein. The catheter waz then removed and the abdomen
The
sample.
vein was cannulated
catheter of 0.96 mm
Phama,
blood
,cfcrencc
was also inserted to
opened via a midline incision, and the superior mesenteric
under
ðyl ether anesthesia. the portal vein was exposed after external
artery cathether
shunts was
et al. (12).
(New England
Briefly,
Nuclear,
Bos-
of 15nm in diameterweresuspendedin
10% dexrran. After sonication for 10 min, 0.15 ml miero-
either 2 to 3 h (chronic 2-3 h) or 18 to 24 h (chronic 18-24
spheres suspension (=@I @M microspheres)
h) after the final dose of propranolol. A fourth group of __.. .____. _^^“:.._rl .“._) __ ;‘z-ah^ (saline) by garage for 10 conscc-
and flushed with 0.4 ml saline into the portal venous ~1%
utivc days. Ten days &cr
riod of 20 s.
wrtal
vein stenosis. the other
two groups of rats r”ccived o single dose of prapranolol75 mg/kg by gavage. Hemodynamic
tern via the superior
mesenteric vein catheter “vc,
a pe-
The animals were then killed with pentobarhital,
and
individual
studies were pertarmed
were iojected
organs were dissected ““t. The radioactivity
of
either 2 to 3 h (acute 2-3 h) or 18 to 24 h (acute 18.-24 h)
each organ and the reference blood sample were counted
after proprznolol
in a gamma
ndministration.
received prapranolot
The last group of rats
4000,
75 mg kg-’ day-’ by gavuge smrting
5 days after portal vein stenosis and then continuously
for
scintillation
Intertechnique,
eoonte,
P&i,,
(Lompteur
France).
Gamma
Adequate
sphere mixing was assumed when the differene
microa: radio-
5 consecutive days. Only portal prcr~ure and portal-sys-
activity between the left and right kidney was below 10%.
temic shunts were measured 2 to 3 h after the final dose of
Five animals did not meet this requirement
propran”l”l
jected from analyses.
In the second part, measurements
continuous
dally portal
pressure
we.e taken in I6 conscious. unrestrained
Cardiac formula:
“utpur
(CO)
CO (mllmin)
was calculated = [radioactivity
rats. Three days before portal vein stenosis, rats received
ference sample radioactivity
enher prooranol”l75
diac index (CI)
mg kg-’ day-’ (n = L,) or placebo (n
= 8) by gavagc and then continuously days. Portal pressure was neasured
CI (mlmm-~~100
:or 3 consecutive
and recorded
every
24 h after initial portal vrm itcoosis.
g-t body wt.) = CO/100
gional blood tlow was calculated
tributary
“ndei
diethyl
ether anesthesia.
a
blood
splren, stoowh, creai
blood
flow
.
iniected
(6Tp.F)
small howl,
flows.
Portal
Car-
formula:
g body wt. Re-
according to the follow.
in8 formula: “r8an blood flow (ml/min)
Blood f7ow and mcsenreHc-.rysrrmic shunr rnemurenwnls. All rntr were fa\ted I8 h before the studier hilt had to water.
injected (cpm)irc-
x 0.8 (mllmin).
was derived from the following
tivity (c”mYradioactivitv
free izce”,
@pm)]
and were re-
by the following
= [organ ,a
(corn)1 x CO.
ioacPortal
..I.
was taken
as the sum of
colon, melentcry
tributary
blood
ftcw
and panwas ex-
pressed in ml~min~‘~100 g-’ body wt. Systemic vascc!*:
?i5
resistance (SVR) was calculsted according to the following formula: SVR (dyws-cm-’ x IO’) = [mean attetwl pressvrz (iMAP (rrmlig)) x aO]/CO. Portal tributary “2s. cular tesistance (F WR) ws calalated as follows: PTVR (dyn.s.cm-’ x III’) = ([?AAP - portal pressure (PP (mmHg))] x BO)WTRF. Hepatocollateral vascular rcsistance (HCR) was :alculated as follows: HCR (dynwtr5 x ld) = (PP x gO)/PTBF. Hapatic fraction of ponal fiow (HFP) was calculated as follows: HFP = PTBF-(PTBF x MSS%) expressed as mlmin-‘,g-’ Iwer wt. Total hepatic blood flow (THBF) was calculated as follows. THBF = HFP + hepatic anery hlood tlow expressed as ml.min-‘.g-’ liver wt. Fractional hepatic blood flow (FHBF), which was the percentage of cardiac output reachirg the liver per mm. was calculated as follows: FHBF(%) = (THBRCO) x 100. In order toobtain a b.t ter Statistical analysts tot hepatic artery blood flow, hepatic Raction of portal flow, total hepatic blood flow. and fractional hepatic blood flow, we combined all tats recet”. ing early chronic propranolol administration s:arted before portal vein stenosis (n = 12). all rats teceivmg acute propranolol administration (n = I?) and compared them with the pldll?bo and the normal group. The degree of mesenteric-systemic
shunts (MSS) “2.i
calculated using the following fotmula: MSS (%) = [lung radioactivity (cpm)/li”er + lung radioactivity (spm)] x 100. The reprcducil~ility of MMS was measured in three consciaus unrestrained portal hypettsnsive rxs The coefficient of “atiabJity (xcand tneasuretttent - first measurement) x lOO/tirst measurement) was 35 f 14%
LX,+ purt,,l ,,rerru,e ,nell~tvw,te,tl. After 3 days of e thcr proprx~olol or placebo :xdwinistration. a media I:qx!rotomy war performed under diethyl ether anecthesia. Chronic cannulation of the portal “em was performed a~ previously dcrcribed (!3). A silastic tube of 0.M mm cxtetnal diameter (Dow Corning Cotporatmn, MI, U.S A ). connected to a 0.96 mm po!“ethylene catheter ws inserted into a small ileai vein and then gently advanced to the bifurcation of the supenor mesenrxic vein and splemc vein. Through the ,““ctmn of the .~I.stic and polyethylene tube, the catheter “as Faxed to the ntesentery with 3-O silk. and baseline portal pressure was measured and recorded with a pressure moni!or (Philips CM 1311.The Netherlands). After obtaining the baseline partal pressure. penal vein stenosis was performed as described xbove. The abdomir,al wall was closed with cat@, and the polyethylene
catheter
was brought out thrcwgh a
cubcutaneous tunnel and fixed to the ammal‘s neck. Iite tats were housed in individual cages with free access to food and water. Pottal ptexure was mez;ured every 24 h for 3 days following initial portal “em stencs~. Vahd pressures were :btained *hen pressure tracing showed a :apid nse followed by a stable plateau with slight respiratory variation. and blood could be easily aspirated. Two tats itt each group ‘x..rc excluded since they dad not meet these criteria.
Results were expressed as mean + S.D. One-way anal“sis of variance with Dunnett‘s correction of multiple
216 comparison was used for statistical analysk. Correln:mns were examined by linear regression. p values < V.dS were considered statistically significant.
Results Aloodfloa nnd merentr-,~cic-sysremicshunr rnemvremen,~ Results of hemodyrmmic values am rhow” in Table 1. There were significant differuxa in portal pressure, mesenteric-systemic shunts, and hemodynarnic values between normal rats and portal vein stenosed rats receiving placebo. Mea” arterial ,,ressure wes not altered by ci!her acute or chronic proprsnolol administrm;on in rats compared to rats receivittg placebo. I” rats receiving cbro”:~ propranolol. cardiac index, heart rate. portal pressure, port;: tribzry blood flow, and me:en!s: c-s::z!cmir: shunts measured 2 to 3 h after the final dose of propranolol wre significantly reduced compared to rats receiving placebo. Systemic and portal tributary vascu$r resisrnnce increased rignificantls in rats receiving chronic propranoIxrbo group. On the other band, 101 compared rvbiler uodynmmc changes were four d in rets ?!O? single dose of propranolol compwed to the
! I! .
(1t’l t a
plac? o group. e”ll’ rc-systemi: inns.. 2 tu 3 ‘, ceiving a .r;,gle dynamic WI les
there was no signitsant difference in messhunts between the two groups. Fortheratrer proprairolol administration, rats redose of propranolol demonstrated hemosimilar to rats receivmg chronic proprano-
!L?!. At the same lime, mesenteric-systemic shunts were siguiiwantiy higher in rats receiving a single dose of propranolol :.nan in rats receiving earl! chronic pro~ranolol. Eighteen to 24 h after proprarnlol administration, compared to the placebo group. ran receiving chronic propranolol showed a sigi.ificant reduction in cardiac index, bear1 rate, po::al pressure, portal tributary blood flow,
and mesenteric-systemic shunts. Portal tributary vascular csistance increased significantly. I” rats receiving a sin. gle dose of propranolol. cardiac index. brat rate, portal pressure. and portal tributary blood flow measured lg to 24 h after prapranolol administration were also significantly reduced compared to the placebo group. At the same time, mesenteric-systemic shunts values were “early identical in these two groups and were without stati&aI significxxe. Moreover, 18 to 2,4 h after propranolol administr:ttion. portal pressure and mesenteric-systemic shunts values were signifkantly lower in rats that had received chronic propnmolol than in rats receiving a single dose of propranolol. In rats receiving propranolol for 5 consecutive days after pan-! vein stenosis, portal pressure 01.8 f 1.2 mmHe. li < 0.01) decreased sieoificantlv cun&ed to the placebo groop but there was no signif5 cant din’erence in mesenteric-systemic :;hu”‘-s (76 + 14%)
_.
between
,
I
,
the two groups.
Among rats receiving propranolol, either acutely or chrcnically, tbcre was a highly sign;ii.a”t correlation beiwee” cardiac index and portal tributary blood flow (n = 24, r = 0.84, I < 0.001). However. in rats rsceivine txopranolol, no correlatb-n was found between portal Pressure and portal tribuhry blood flow (n = 24, I = 0.04.p = -I
0.85). Hepatic artery blood flow, hepatic flow. total hepatic blood flow, and blood flow values are shown in Table nosed rats receiving placebo showed tions in hepatic fraction of portal flow,
fraction of portal fractional hepatic 2. Portal vein stesignificant reductotal hepatic blood
flow, and fractional hepatic blood flow compared to normal rats. On the other hand, compared to rats receiving placebo, portal vein stenased rats receiving chronic prapranolol showed significant increases in hepuic fraction of poRal flow, total he@ic hepatic blood Bow
blood flow, and tiacticmal
PROPRANOLOL
IN PREVENTING
PORTAL
WPERTENSION
217
s-udy. prop:ioolol Portal pressure changes after portai vem stenosis are shown in Fig.
1. Compared
to rats receiving
placebo,
ba.eline portal pressure decreased sigmficantly ce.ving propranolol
m rats re-
(5.8 + 1.2 vs. 7.3 f 0.8 mmHg.
p <
O.fl5l. On the 1st. 2nd. and 3rd dav. resoectivelv. ,a
after
1
portal
vein stenosis. rats receiving
rig,nificantly
lower penal
prcswre
propranolol
showed
than in rats receivmg
placeho (20.1 -r 2.7 vs. 2,;.2 + 2.2 mmHg. y < 0.05, 1X.3 f
1.5 mmHg. p < 0.01: and 16.6 +
1.6 vs. 21.7 f
I 7 vs.
was aJminis:crcd
by oral-gwric
vage which i: similar to the clinical sitution. propraoalz
or:d
in our rats, however.
differs from the
dose used in cl.nical investigations since propzmolol
me-
tabolism markedly differs amongrpenes. In the present study. a redwion porn-systemic
of tix percewqe
of
shunts was only observed in rats receiving
early chrome propranolol
begun &fore
portal vein steno-
sis. This effect was noted either 2 to 3 h or 18 to 24 h after the final dose of propran~:ol.
lo contrast. acute ado&w
trarion or contmootts administration
20.3 2 1.0 mmHg, p < 0.01; respectwely).
ga-
The dcse of
of propranolal
after
portal vein stenosis lowered portal pressure but had no etfeet on the percentage of portal-systemic over. hemodgxmtic
last dose r: proprwtolol In the present study,
wehave ciearly
early and chronic propranolol severity of portal portal-systemic Our
hypertension
of rats. rire
stndieq (o.10) and wppat
pothesis that early pharmacotherapy opment of prtal-systemic
of
vein steno&.
from a small number
mn~is,eo, with predow
Ihat
reduced the
and the developmen:
shunts in rats with portal
results. obtained
aniaals.
demonstrated
adminisrration
the hy-
prevents the de-&
shunts m portal
hyperteasive
In previous studies experiments were performed
under general
anesthesia
ments were obtained demonstrared
and no blood
(9.10).
flow
Furthermore.
mearoreit was not
whether the beneficial effects were a result
of chronic or acute administration
of propr~nolol.
In thtr
shunts. More.
values measured 18 IO 24 h atier rhe were similar
in rats recekang
chronic propranold
and in rats receiving a single dose of
propranolol,
portal
while
prescore and portal-systemic
chrmrs li’eie lower in mts recen’ing chrome propranolol ihan In rats receiving a single dose of prqxanolol.
The
lot’ percentage of shunting observed in rats receiving early and chronic propranolol oasis was probably
begun before portal vein ste-
due 10 a limitation
of the initial
c.edse in portal pressure whnch onmediately tal vein stenosis, i.e., pressure rea&ed
in rats receiving
24.2 mmHg
I day
in-
follows por-
placebo.
portal
after portal vein ste-
nosis. whereas it reachrd only 20.1 mmHg in ra:‘, receiving p:opranolcl.
In addition.
Gstec on the 2nd and3rd prewmabiy panolol portal
admmistration. hypertension
this beneficial
efLct
pcr-
day after portal vein stenosis and
on the following
days doe to continuous pro-
In other words, in this model of
in rats, the development
of p-anal-
systemic shunts depends mainly on t’le imtial elevattm
of
portal pressure. Similar observations have been pre\ IOUIy demonstrated
in rats vdth portal vein stcnosis (14 :5).
la these previous stt dies, a significant found between mesenteric-systemic
correlation
eter of portal vein stencsi~. and presumably, rise in portal pressure. significant relationship teric-systemic
the initial
previous studies also reported
a
bera een the percentage of mesen-
shunts and the value of portal
measured 2 weeks after portal \ein contrast,
was
shunts and the diam-
there was no correlation
pressure
stenosis (12.14).
In
berween splenic-gys-
temic shunts and the diameter of stenosis or the degree of portal hyperLtsion rplenic-syswnic
(14). The tack of correlation
shunts and portal
between
pressure may be re-
lated to the extensive splenorenal
shunting ;vhich occurs
with a moderate
hypertension.
:iiij:,
;ii::e
degree of portal
:EPC:C portA
bypencorioa
merenieric-systemionhuntsto In :his study, propmnolol
decreased portal
cardiac index. and portal tributary wiving propranolol,
In con-
ii necs.siary for
develop. preswre.
blood flow. In rats re-
since portal tributary
blood flow sig-
H.-C. UN
218
et at.
nifirantly correlated with the cardiac index, while portal
blood flow was not altezcd by propranolol
admin,stration,
prcssurc
wherea*,
increased
showed
blood tlrw.
no
correlation
with
portal
the decreased portal tributary
not only due to a decrease in cadiac outpa increase
in portal
been postulated
tributary
tributary
blood flow was but also to an
va~cuk+r resistance.
:hat the mcreaxd
portal tributary
activit)
or to the ,9,-bkxking Although
to 3
I >‘ter ‘ ither
pr~van~~lol
property
vascu-
chronic
cam increw:
group.
in hepatocollateral
Desprte the short half-life
vascular resistance
total
chronic
the liver
hepatic
hepatic
fraction
In rats receiving oI portal
flow
was also increased
ndmini~trati.m,
10
mals. From
the
shunts in these portal
precent
chronic proprarlolal portal
hyl rrwxion
study,
hypertensive
we coscludcd
administration
stall persisted. In the presence cf hypertensive
nuiui aiwr vrai administratmn
of propra-
aniearly
of ponal-rys-
effects probably
the systemic and splanchnic hemodynam-
thsr
reduced rhe degree of
and the deve!opmont
administration.
rats. a decreased ‘first pass’ heparic elimination
of par-
tal flow was in accordattce with the lower degree cf mes-
we at~o noted
shunts in these portal
by
suggestmg a better
temic shuctr in portal vein stenosed rats. The:t
ic effects of propranolot
placebo.
The increased hepatic fraction
that. 18 to 24 h after either acute or chronic propranolol
the penal-systemic
flow in-
with the rats receiGg
blood
propranolol
hepatic perfusion.
has been previously
patients (21).
enteric-systemic
of propranolol.
of propranolol,
propranolol,
after
of
there have been similar signifi-
to 2tJ min after intravenous administration
*caching
flow
In
chronic or acute oral administration
vere higher than in thk placebo
previous s! ‘ties (18,lU).
Thus,
2
blood
An increased fraction of the
in ciirbottc
creased in comparison
the mean
vz~scular resistance mearsred
hepatic
sdministratiun.
output
demonstrated
of propranolal
not s atistically significant.
values of he ~tocollaferal
cardioc
It has
lar resistance in rats is due to an unopposed a-adrenergic (8.16-18).
fractional
proprenalol
beneficial
resulted from a limited initial increase ill
portal pressure immed’ately sis. The application
follr,wing
portal vein steno-
of this treatment in man needs, how-
ever. to be investigred.
may enpiain these bernady-
namic changes. In the present study. we also demonstrated vein stenosed rats receiving Iov.ei total hepatic blwd tlow,
and fractional
rats. Although
placebo
+-!
+rtal
had a significantly
flow, hepatic fraction of portal
hepatic
blood
flow than iat normal
not stattstically significant,
the mean value
rf hepatic artery blood flow in portal vein stenosed
rats
receiving placebowas higher than in normal rats. A similar observation has been reported in a previous study (20). Consistem with previous result (8.16,18), in our investigation
in portal
vein stenoscd
rats, hepatic
artery
Dr. Lin WE supported government.
anli ‘ram
by a fellowship the Veterans
from the Frerlch
General
Haspital-
.
and iCd!ional Science Council. Taiwan. R.O.C. held a fellowsi5p from the Fonda&n poor la Recherche hl.Sdicale. This work was presented in part at the 41st annual meeting of the American Association
Taioei.
Dr. Soubrane
For The Study of Liver Disease, Chicago, IL, U.S.A., November 3-6, 1990; and was published in abstract form (Hepatology lY90,12:874).
PROPRANOLCL
IN PREYENTING
l’0RTc.1.
HYPERENSIC)N
21’)